Biological Effects of Radiation Flashcards

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1
Q

What are the three electron interactions with matter?

A

Ionisation
Excitation
Heat production

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2
Q

What is the energy loss of an electron for each ionisation caused?

A

34eV

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3
Q

State and explain the three light production methods on irradiation

A

Fluorescence: prompt light emission
Phosphorescence: delayed light emission
Thermoluminescence: light emission when heated

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4
Q

Explain how indirect damage can arise from radiation.

A

Action of radiation leads to excited macromolecules (RH -> RH*) and then to the production of free radicals R· and H·

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5
Q

Which is more likely at diagnostic levels: direct or indirect action?

A

Indirect

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6
Q

Define Linear Energy Transfer (LET)

A

LET is a measure of the rate at which energy is transferred to the medium (ie. ionisation density along the track of the particle)
A more penetrating beam has a lower LET

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7
Q

Define Radiobiological Effectiveness (RBE)

A

RBE = dose of 200kVp x-rays/dose of other radiation to give same biological effect

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8
Q

What does RBE vary with?

A

Dose
Dose rate
Fractionation
Physiological conditions (eg O2 concentration)
Biological species
Biological end point chose for comparision
Time after irraditaion when measurements made

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